Candaith cannot decipher the letters you recovered from Orcs in the Lone-lands, but he knows a Ranger who might.
'The letter you discovered within the Bleakrift is also written in the Black Speech -- we need to know the orders contained within each of these letters. I am not a student of the tongue, but there is one of my kind who is.
'Out of Bree, north along the Greenway and east of the road, there is a cabin where Rangers gather. Saeradan often keeps vigil there; he is a friend of mine, and he may know enough of the cruel sigils to make sense of at least some portion of these orders.
'Travel to Bree-town. From the West-gate of Bree travel north along the Greenway until you spy the Ranger cabin among the trees east of the road. The cabin is quite near to Thornley's Work Site. Find Saeradan and ask him to translate these orders. May haste speed your errand!'
Saeradan is at the Ranger cabin along the Greenway, north of Bree and east of the road, near Thornley's Work Site.
Candaith gave you both sets of orders you collected and asked you to show them to the Ranger Saeradan.
The Ranger Candaith is at his camp at the foot of Weathertop.
Saeradan revealed that Orcs calling themselves Uruk-hai have come north to spy out the land and discover why their northern cousins are moving southward. He asked you to return quickly to Candaith and warn him of the danger.